Automatic telephone system



APlil 14, 1931- H` MFRu-:NDLY 1,800,787

AUTOMATIC TELEPHONE SYSTEM Filed June 23, 1927. 6 Sheets-Sheet 'l Aufn- 51u11? Fing Ally- EPTE Mw m3@- H. M. FRIENDLY y?. 1

AUTOMATIC TELEPHONE SYSTEM Filed June 23, 1927 6 Sheets-Shea?. 2

` 3 g N` R f N" @i RZSaTr-Ic InvEnnF- Herb EF1-M-Frendly pri M, l931- H.M. FRIENDLY AUTOMATIC TELEPHONE SYSTEM Filed June 23, 1927 6 Sheets--Sheetv T5 mmmmml -muuu H ddnm m OL/IIIIH u l2 mFTN Eur@ -m55 Nunn@ Invannr- HE Eri-PI-Frendhz;

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April 14, 1931- H. M. FRll-:NDLY

AUTOMATIC TELEPHONE SYSTEM Filed June 25, 1927 6 Sheets-Sheet 4 Invenm" Herb Eri-NFH MNM.

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H. M.. FRIENDLY 1,800,787

AUTOMATIC TELEPHONE SYSTEM Filed June 23, 1927 6 Sheets-Sheet 5 April M, 1931.

NNN. )mlm April M, 1931. www? H. M. FRiENDLY AUTOMATIC TELEPHONE SYSTEM Fild June 2:5, 1927 s sheets-sheet e Else- Trk AHH.

Patented Apr. 14, 1931 UNITED STATES PATENT OFFICE i HERBERT M. FRIENDLY, F CHICAGO, ILLINOIS; MILTON S. FRIENDLY AND CENTRAL TRUST ooMPANY or DEonAsnn Application filed June 23,

. Objects ,"lhe vpresent 'invention 'is particularly directed .tothe switch trains used in linking connections from local subscribers lines to local subscribers .lines and from toll operators switchboards of the local exchange and also remote points to local subscribers lines of said local exchange.

A salient feature of the present invention is the employment of a so-termed combination local 'and t'oll selector which will cooperate with a so-called combination local and toll connector or final switch. ACombination local and toll connectors adapted for cooperation with antecedent local and antecedent toll selectors depending upon the origin of the call have been used heretofore and are well known. However, the combination local and toll connector of the present invention while having the generalpurposes of those well known incorporates details and functionswhich are new, so far as I am aware.

The employment of the combination local and toll selector of the present invention which cooperates with antecedent specilic local and antecedent specilic toll selectors enables selectors of a single type to be employed in a group immediately antecedent to the connectors, in place of groups of selectors which are each' (group) specic to the origin of the call, as heretofore employed, so far as I am aware. The combination local and toll selector of the present invention thus admits-of providing'a single group of selectors, each commonly cooperative directly with the combination local and toll connectors, in place of two groups, each group From the last foregoing statements it will' be understood that th'e present invention contemplates that regardless o whether the call ILLINOIS EXECUTOBS OIF SAID, HERBERT M. FRIENDLY,

AUTOMATIC TLPHONE ShYSTEM 1927. Serial No. 200,832.

is progressed over the local selector train or the toll selector train it may route over the same iinal selector and connector in attaining connection to the called line.

Another 'feature of the present invention is the toll operators switching cord-pair,

which provides for disconnecting or exclud-- ing the impulse callingdevice from the last connection progressed, automatically responsive to the completion of setting the wipers of the connector upon the terminals of the called line, whether the called line is found busy and thus barred against seizure, or is found idle and in condition for seizure by the connector.

A feature of the toll operators switchin cord-pair is the arrangement by whic through the agency of specific cord-pair ringing keys, the method of initiating rinving on the called line may be predetermined; that is, whether the called line will be rung upon intermittently automatically responsive to its seizure by the connector or whether the said character of ringing will only start at the will and under the direction of the operator after the seizure of the called line by the connector. Also, that the elected predetermined method of ringing may be changed by operating the corresponding specific said ke any time before or after the extension of t e call is started andbefore the called line is seized by the connector, and further, that in the event the operator has elected to have the said ringing start automatically responsive to. lthe seizure of the called line by the connector and the called line is encountered busy, preventing the seizure by the connector, the method of initiating the ringing will be thereupon changed to start only upon the will and under the direction of the operator by operating the corresponding specific said key, in the event the called line becomes idle while the connector is retained inv selective relation with it.

The toll switchboard operator will be ap- Erised of the busy condition last referred to y means of a specific so-called busy-tone applied audible in her head telephone set (through the cord-'pair listeningl key) and the called line becomes idle. However, the

connector will not seize the selected, now idle called line under the condition unless by a directive operation by the operator for starting the ringing onthe called line, which if the called line has become busy in the mean time, will operate to ire-apply the said speciic busy-tone and re-start the said flashing of the supervisory lamp. if the selectedv called line is still idle when the operator directs the starting of the ringing after the busy-tone and the dashing terminates the selected called line will be thereby seized by lthe connector and the ringing thereonstarted. The ringing on the called line is always automaticallyintermittent until the calling party terminates the initiated condition of the call or the called .party responds. However,v the frequency and inherent character of the said intermittent applications of ringing current will vary dependent upon whether the call is initiated by the local subscriber or by a toll operator. The applications of ringing current when the call is initiated by a toll operator may, as indicated, be more rapid and also may be variablyl spaced so that the called subscriber will be thereby 'apprised through the operation of a specific call bell as to the origin of the call and inspired to more hastily respond to it if it is from a toll operator.

There are a number of other features in the system believed to be novel and these will be specifically set forth in the descriptions to follow, or will he apparent in view of the descriptions.`

The system .chosen to, elucidate the invention is only an exemplary embodiment; the invention being capable of various expressions, either as an amplification or as a c urtailment, without departing from the spirit thereofs in view of the scope defined by the subjoined claims.

` Drawings With reference to the accompanying drawh in s:--

ig. l shows a toll operators switching cord-pair9 and circuits common to a plurality of such cord-pairs as indicated by the vertical lineextensions. A trunk-terminating jack J cooperative with. the right-hand plug P of the cord-pair is shown on the right.

lr'iig. 2 shows a toll-line-terininating first selector A and a trunk-iine-terminating lirst selector B, havin common access to the toll second selector p taining Fig. 2 joins o`n the right of the sheet' in Fig. 3. The sheet' concontaining Fig.`1,so that the lines extending towards the adjacent margins register.

' Fig. 2A shows a toll line and operators switching-cord apparatus9 the toll line exlending to selectoritV of Fig. 2. Fig. 2A.

innerer joins above the sheet containing h t e adje that the lines extending towar s cent margins register.

Fig. 3 shows a tolll second selector@ commonly accessible from the selectorsA and 'B and other selectors of their respective groups.`

third selector D which is one of a group ac cessible from the group containing selector C; selector D itself having access to combination local and toll connector E and others of its group. rIhe selector D and other selectors of its group are also accessible from,

the group containing local second selector F. rll`he sheet containing F ig. 4 joins above the sheet containing F ig. 3 so the lines eX- tending .towards adjacent margins register.

Fig. 5 shows a combination local and toll connector E of which there is agroup having, common access to called lines. The sheet containing Fig. 5V 'oins to the right of the y sheet containing Fig. 4. so that the lines extending `toward the adjacent margins register.

Fig. 6 shows a preferred modification of selector D for use where only part (three last choice in the exemplary embodiment) of the selector group eontainin selector D are conibination local and to and the balance (seven) solely local.

Fig. 7 is a diagram showing the preferred arrangement' of the local and toll selector trains wherein part ofthe connectors (seven) are local and part (three) are combination local and toll, the preferred embodiment of the combination local and toll selectors being as shown in selector D with'the disclosure in Fig. 6 introduced.

Equipment y The telephones T and T5 are of the well known automatic series common-battery type.

The selector A is of the well known Strowger general class, modified in accordance with the present invention.

The selector B is ofthe well known Strowger general class (sometimes termed a Powellselector) modified in accordance with the present invention only as relates to the lower armature'and cooperating springs and circuits including the tone source T2 of the.

lift

tion employed in so-called rotary line switches wherein the wipers are advanced upon the deenergization-of the motor magnet and which has no specic' idle position to which it restores. i

The selector D is of the well' known Strow- Vger general class (sometimes termed a Powell selector), modified in accordance with the present invention only as relates to the added lower set of contacts of the left-hand relay and the added-second (from the top) wiper. The, connector E is of the well known Straw er side-switchless combination (nonrotary local and toll general class, modified in accordance with the present invention.

The line switch L may be of the -well known Keith or Lamb'general class, or other/well known class of line switch orfinder switch.

l The 'local first selector M and the local second selector F may be of the well known sotermed Powell type.

Well known switches referred to are illustrated in the third edition of Hersheys Automatic Telephone Practice as follows: Powell selector, page side-switchless connector, page 38; Keithyclass line switch, page Li5; rotary (Lamb class) line switch, page 54.

0 parution Initiating @all from `telephone T to telephone T5 Upon the calling subscriber iniating a call by removing his receiver from the 'switchhook, the line switch L'will operate to sel-ect the first idle first selector M. The telephone r number of the called line being 11111 the calling party will first' operate his calling device 10 in accordance wlth iirst digit 1 to set the first selector M into connection with the first idle second selector F. He will next operate the calling device in accordance with second digit 1 to set the second selector F in connection with first idle third selector D.

A He will next operate the calling device in acby reference to the said books of Hersheys as'follows: line switch L, pages 41 and 53; selectors M, F and D, page 59.

The calling device 10 is now in series with the windings of line relay 501 over an obvious path, since the first two relays counting from the left in connector E are deactuated, and slow-releasing release relay 502 is actuated and the release trunk 505 is grounded by armature 506 to maintain the antecedent switches in seizure.

Responsive to the calling party sending the fourth digit 1 the relay 501 will momentarily retract its armature 508 causing ground thereon to be applied through attracted armature 509, off-normal spring 510, winding of slow-releasing series relay 512 to the vertical magnet (designated Vert. M.), causing the shaft 514 carrying the wipers 515 to 517 to be raised into alignment with the first level of bank terminals.

At the time the shaft 514 moves off-normal the spring 510 is disengaged and the spring 518 is connected in lieu thereof, having in mind that the armature 519 of relay 512 is now attracted.V However, this armature 519 retracts consistent with the releasing characteristic of the relay 512 following the digit impulse, so that when the impulse constituting the fifth (last)- digit is sent ground will be applied from armature 50S, armature 509, spring 518, armatures 519, 520, 521 to the rotary magnet (designated Rot. hi), the latter magnet rotating the wipers 515 to 517 in one step into engagement with thebank terminals 525 to 527, respectively. The winding of slow-releasing relay 528 being in multiple with the winding of the rotary magnet, will operate.

In this connection, it will be understood that had the fourth digit been larger than 1 the armature 519 would sustain attracted until after the termination of the last impulse of the series constituting the digit, and in the same manner the armatures of relay 528 will sustain attracted until after Athe termination of the last impulse of the series constituting the digit. The operation of sideswitchless connectors of this general class is set forth on page 36 of the before mentioned book of Hersheys.

UaZZed Zz'ne Edle n callfrom subscm'er The called line being assumed idle, battery potential derived through the well known line switch cut-ofi relay 530 will be on bank private terminal 525 so that when armature 532 retracts a circuit path from grounded battery, winding of relay 530, terminal 525, wiper 515, make-before-break spring 531, armature 532, outside winding vof" wiper-switching relay 534, armature 535, make-before-break spring 536 to the grounded release trunk 505, the relay 534 actuating and locking by its inside winding through armature 538 to the release trunk. The uper inside armature of relay 534 will apply usy 'ground over wiper 515 to terminal 525 to operate the relay 530 and guard the line called against seizure by any other connector.

Ringing called line in call from subscriber Ringing current is now applied from 'grounded source R5, armatures 539, 540, 541

the condensers in series with said bells. However, upon the party at telephone T5 responding by removing tlievreceiver off the switchhook, causing' a conductive circuit to Abe 'formed over the traced path to telephone T5, the relay 546 will actuate and lock its inside winding-through armatures 547 and 548 to the release trunk, thus completing the talking path over the heavy conductors between the telephone T and T5. The back-bridge relay 549 will actuate and reverse the direction of current ow over the calling line responsive to the relay 546 actuating, the' windings of relay 549 now being in series with the telephone T5. l

allcrl busy in call from subscriber Had the called line been busy and ground potential therefore existed on bank terminal 525 at the time the wiper 515 was first set thereupon the connector would not then be enabled to seize through the actuation of relay 534 because there would be no idle-battery applied over the wiper 515 to energize the outside windin of relay 534. Further, the ground received over wiper 515 will be applied through spring 531, armature 532, make-before-break spring 550, armature 551 to the winding of busy relay 552, thelatter relay actuating and locking by its armature 535, spring 536 to the release trunk; relay 552 being disabled from -deactuating until the ground is removed from the release trunk responsive to the calling subscriber hanging up his receiver. During the time relay 552 is actuated specilic busy tone from source l*s is applied interruptedly through vthe agency of interruptor I"5 through armatures 553 and 554 to talking conductor 555, audible to the calling party.

Restoralicn of switches by calling subscriber The connector and'dependent antecedent switches can be restored at any time after the connector isseized by the calling subscriberreplacing his receiver on the switchhook ytoopen theenargizing circuit for the line relay 501., in turn causing the relay 502 to deactuate, closing the obvious circuit for the releaseI magnet (dcsignatedltel. hl),

recare? whereupon the shaft 514 will be 'restored to i its normal position. y @all from toll switchboard tc telephone T5 tuate and apply ground from its armature 204 to the release trunk 205. However, the release trunk was previously grounded through auxiliary spring 17 at the time plug P was inserted into jack J. The guard lamp 18 will thus glow, there being a plurality of jacks similar to J and guard lamps similar to@ 18 (not shown) multipled at other operators; toll switchboards.

tent ringing on called line lnthe present call it will be assumed that,

the ringing on the called line will be deferred until the operator desires to start the automatic intermittent ringing. Accordingly, the speciic ringing key 19 will he operated way-down and held latched in its intermediate position by the well known shift-plate (not shown), however, the key plunger (not shown)I is retracted far enough to disengage the' way-down spring 20. Ground from spring 21 energizes relay 22. The slow-releasing rela 23 is actuated whilgthe spring 20 is groun ed to disable the shift-plate tripmagnet (designated Trip. M.) while the operator has the key 19 held manually operated way-down. The lower armature of relay 22 energizes the upper winding of slow-releasing relay 2 4, while the armature 25 of relay 22 appliesground through armature 26to the winding of slow-releasing relay 27, the latterl relay actuating and by its grounded armature 28 operatively energizes the relay 30 and causes itto lock to armature 25, the relay 27 deactuating consistent with its releasing characteristw. Armature I31 in attracting serves to unlock any relays corresponding to 32 of the specific operatorie position which maybe actuated at the time relay 27 is caused to actuate.

i Toll operator may start automatic iniermilas l los`

ne y

When relay X30 actuates, and after arina- `ture 28 has thereafter retracted, ground from armature 28 is applied through armature 34, spring of key 35, make-before-break spring 36, ke' spring 37, conductor 38 to the windlng o relay 32. The latter said relay actu-- ates' and prepares a locking circuit for itself at armature 39. Due to the key -19 being lked between ground, spring 13 and the traced circuit including conductor 15, and winding of relay 201, and the relay 12 is deactuated. Lamp 10 is extinguished and 4operating lamp 42 is glowing.

A circuit path can now be traced from` `grounded battery, winding of relay 43 (which is non-susceptible to the ringing, current source G) armature 44, ring of plug P and Jack J, talking conductor 45, make-beforei break spring 205, secondary of tone transformer T2 to ground. Relay 43 actuates, followed by its dependent slow-releasing relay 47. Attracted armature 59 opens the ground path to key spring 37 and becomes in a locking path from armature 39 to armature 28. The operator may, by manipulating her listening key L, perceive the tone from source T2 indicative that the calling device 40 may now be operated adective to the first selector B. A locking circuit is closed from armaturel 48, armature 49 to the winding .of relay 30 to maintain the latter said relay actuated in the event relay 22 is deactuated, as will appear presently.

Armature 2 8 having retracted, its ground is applied through armatures 51 and 52 to glow the ringing lamp 53, which latter lamp is companion to the key 19to prompt the operator that the specific key 19`Was operated and that ringing on the called line will be deterred until she at will starts it by operating ringing key 55', for example. The

lower winding of relay 24 isV now locked through armatures 56, 59, springs' 36 and 35,

armatures 34 and 28 to ground.

The spring 2O bein-g free and relay 23 being deactuated a circuit can be traced from the grounded armature 48, armatures 57 and 58 to the 'trip-magnet for shifting the shift-plate to release the key Y19 to normal position, followed by the'deactuation of relay 22. At this time relays 32, 43, 47,24 and are actuated; lamps 18, 42 and 53 are'glowing and the cord-pair key 19 is in normal position.

Toll Operator @attends caZZ-Fzrst'ldjz'gz't The operator may now` operate the calling device in accordance with the irst digit 1 of the number of the called telephone T5,

which will cause the impulse relay 201 `to with the rst level of bank terminals. At

the time relay 209 actuated ground from the release trunk was applied through off-normal spring-217 to operatively energize the marginal interrupter relay 220 and lock it through its armature 221 to the release trunk. The relay 209 will retract its armature consistent with its releasing characteristic following the impulse (or the last impulse of @a series had aseries been sentlcausing the rotary magnet (designated Rot. M.) to be operatively energized through the ott-normal spring 217, armature 221 to the release trunk. This will cause the shaft 212 to rotate the Wipers 213 to 216V to set them upon the first set of bank terminals 223 to 226, respectively, of the vfirst level.

At the-time the rotary magnet operated it opened the energizing path for the relay 220, causing it yto deactuate and incidentally disable the rotary magnet. However, if th'e trunk leading to the second selector C `corresponding to, this set of bank terminals is busy by having been connected with by some other selector companion to first selector B or selector A, its release trunk 233 and private bank terminal 223 and multiples will constitute ground potential. Under the latter condition the ground will be applied over wiper 213, armature 237 olf-normal springs to the winding of relay 220, the latter relay `re-operating and locking to close the before stated energizing path for the rotary mag net to cause the wipers to be advanced another step, the successive advancing operations continuing so long as the wiper 213 encounters busy-ground. .However, when the wiper 213 fails to receive ground potential by being set upon the private,bank terminal ot an idle trunk the relay 220 does not then reenergize, and moreover, the lower los Winding of switching relay 239 is thus freed .from ground potential and operatively energizes in series with the winding of unoperated relay 220 which is marginal. This continuesI the talking conductors fromthel tip and ring springs of the jack J to the conductors 231 and 232 `leading-in to the toll second selector C. Relay 43 is main.- tained energized through armature 300 in selectorC to the release. trunk 2,33. The release trunk conductor 205 and the' impulse conductor 15 leading from jack J are continued to release trunk conductor 233 and to impulse conductor 234 leading-in to selector C, respectively.

in selector C is operatively energized over the impulse conductor 234. Slow-releasing release relay302 in selector C is operatively energizedby ground applied through retracted armature 303 and attracted armature 304. Armature 305 applies ground to the release trunk 233 before armature 204 in selector B retracts. vHowever, ground is also applied Relays 201 and 202 in `selector B deactuate,and impulse relay 301 -17 of the jack J.

ahead on the release trunk 205 from spring I Toll .operator'semis second digit The operator may' now operate the calling device 40 in accordance with the second digit 1 of the called telephone number which will cause relay 301 to correspondingly momentarily retract its armatures one. time, applying ground from its armature 307 through armatures 308 and v309, winding of series slow-releasing relay 310 to the vertical magnet (designated Vert. M. causing the shaft 312 carrying wipers 313 to 316 to be aligned with 'the first level of bank terminals. 'At the time relay 310. actuated ground from the release trunk was applied through armature 317, oi-normal springs to operatively energize the marginal interrupter relay 321 andlock it through armatures 318 and 319 to ground." The relay 310 will retract its armature 317- consistent with its releasing characteristic following the impulse (or the last impulse of a series had a series been sent) causing the rotary magnet (designated Rot. M.) to be operatively energized through armature 320 to the release trunk.' This will i cause the shaft 312 to rotate the wipers 313 to 316 to set them upon the. irst set of bank terminals 323 to 326, respectively, of the first level. v

At the time the rotary magnet operated, its armature 318 opened the energizing path for the relay 321,'causing it to deactuate and incidentally disable the rotary magnet. -However, if the trunk leading to the third selector D corresponding to the irst set of bank terminals is busy by having been connected to by some other antecedent selector'companio'n to second selector C or a selector of. the group containing selector F, its release trunk 233 and vthe bank private terminal 323 i will constitute ground potential. Under the and operatively energizes in series with-the winding of unoperatedrelayg321, which ismarginal. c

This continues the talking 'conductors231 l and 232 through bank terminals 3,25 and 326 to the cond ctors 331 and 332, respectively, leading-in o combination local` and toll third' selector D; The releasejtrunk conductor 233 and the impulse conductor 234 iscontinued through bank terminals 323 and 324, conductors 333 and 334, respectively, leading-in to 'v said selectorvD. The attraction of armature 308 disables the vertical magnet. The attiaction of armature 339 operatively enrgizes slow-releasing relay 340' for an object that will appear presently. It also applies ground through armature 341 m wiper 314.

A circuit can now be traced from grounded battery, upper -winding'of linerelay 401,y

armature 402, talking conductor 331, bank terminal 325, wiper 315, upper secondary winding ci? repeating coil, armature 342,

make-beforebreak spring 343, armature 344, S0

outside winding of 'electro-polarized relay 345, make-beforefbreak spring 346, armature coil, wiper 316, bankterminal 326, talking opposite polarity .from ,that of the inside winding which, inoperatively energized in series with resistor 348 when 'the release trunk 233 first became grounded. The relay 345 will therefore not actuate at this line.

Relay 401 actuates under the last described circuit condition, followed by its dependent slow-releasing relay 405, its'armature 406 applying ground to the release trunk 333, so that the latter conductor (release trunk) is now grounded'at three points, since armature 305 infselector C is attracted and spring 17 of jack J also applies ground.' Y

Toll operator sends third digit The operator may now operatethe calling I347, lower secondary winding of repeating f' device 40 in accordance with the third digit 1 of the called telephone number which will Q vcause relay 301 to momentarily retract its armatures as before, but without eiect to the relay 310 since the armature 308 is attracted. However, the momentary retrac tion of the armature 344 in selector C will correspondingly open the traced circuit path llil energizing the rela 401 in selector D. In A view of the well own operation of the concerned circuits in selector D this will cause the shaft-412 to `operate the wipers 413 to 416 into lalignment with the iirst level of bank terminals and into seized engagement with the iiist set of idle bank terminals 423 to 426, leading over conductors 505, 557, 558 and 559, respectively, to connector E.

In this connection, it will be noted that when the switching relay 440 actuates in the well known manner, its lower armature 441,

specific. to the present invention, switchesthrough conductor 334 to wiper 414, effective for operating the converting relay 560 in' connector'E, a circuit path existing from grounded battery, winding of relay 560, con- -ductor 5,57, bankterminals 424, wiper 414,

armature 441, conductor 334, bank terminal 324, wiper 314, armatures 341 and 339, to

ground, the relay 560 actuating to convert the connector E to uses specific to calls'over y the toll selector train as will appear presently. However, it is pointed out that only .when the selector D isseized by a toll selector'as C is ground applied ahead through the arm-ature 441 in selector D to energize relay 560 in the connector The traced circuit path including the out' side winding of relay 345 in selector C, armatures402 and 403 and relay 401 in selector "D is now changed by the attraction of the latter said armatures so that wipersk 415 and 416, bank terminals 425 and 426, conductors 558 and 559, make-before-break springs 561 and 562, 563 and 564 and the windings of relay 501 of connector E are now substitutedfor the windings of the relay 401 of selector D. Relay 501 and its'dependent relay 502 actuate.

Toll operator sendslast two digits The connector will respond to the last two digits 11 sent by the callingdevice 40 in the samemanner as before described with refer-l ence, to the call from telephone T to the telephone T, but only so faras operating the vertical and rotary magnets are -concerned in the actual setting of the wipers on bank terminals'COrreSpOnding to the called line. Certain modied operations peculiar to toll calls will be pointed out. l

At the time relay 528 actuates groundis applied through armatures 565, 566 to oper! atively energize the inside winding of relay 546, the latter said relay locking'l through its armature 547 to larmature 567 (also through armature 548 to the release trunk 505 temporarily), disabling the application of ringing current to the called line.

Called lz'ne enco'u/ntcredZ idle on toll operato?r cal I-f the called line is encountered idle, wherein the private terminal525 constitutes battery potential, this will be applied through wiper 515, yspring 531, armature 532, outside winding of relay 534, armature .535, spring 536, armature 568 make-beforeb reak spring 569 to 'the release`trunk, the relay 534 actuating and locking through its armature 538 to the release trunk. {Armature 570 applies ground through makebefore-break spring 571, armature 572 to the upper terminal of the upper winding of relay 549, the latter said relay actuating to reverse the direction of current in the outside 'winding of relay 345 in .selector C, under which condition the windings of the latter said relay will energize cumulatively and operatively attract its armatures.

Eolufling of calling fleoz'oe responsive to oonmotorsez'ezng Y The attraction 'ofarmature 300 Aof the relay 345 inselector lC causes the toll oper lators switchboard relays 43 and 47 to deactuate in sequence. The retraction of armature 59 opens the locking ground for the relays 24 and 32 and they de actuate; relay 24 deactuating last due toits releasing characteristic. The retraction of armature 48 opens the lookin circuit for relay 30 and Specific operation. of connector on, toll operator calls The actuation of relay 549 completes 'a circuit path from ground, armatures 570, 573,`

574 to the winding of slow-pick-u relay 575, the lattersaid relay actuating.. ue to the armature 574 making last and the stated characteristic of relay 575 the relay 345 in selector C will have time to operate its armature 300 to short-circuit the resistor 348 before thewindings of relay 501 are disconnected. The short-circuiting of the resistor 348 will augment the strength of'cur-4 rent in the inside winding of relay 345 Sulliciently to operatively attract its armatures even if the current in the outside winding ceases or reverses inv direction before the relay has completely actuated. Relay 575 will be maintained locked through its armature 577 to the release trunk 505, which lreceives ground from release trunk 233, the relay 549 being incidentally deenergized by the attraction of armature 576. The relay 501 is maintained actuated by release trunk ground applied through armature 577, lower armature of relay 501 to its upper'winding. f In view ofthe relay 345 in selector C .being actuated, ,the upper Vand lower windings of relay 361 may'b'etraced through armatures 367 and368 342 .and 347, upper and lower secondary windingslof the repeating coil,

wipers 315 and 316, bank `terminals 325 and.

326, talking conductors 331 and 332, armatures 402 and 403 of selector D, wipers`415 and 416, bank terminals 425 and 426. talking cbnductorsf558 and 559, springs 561 and 562, armatures 578 and579, to the disengaged make` contacts of armatures 545 and 541. The relay 361 is thus unenergized.

Starting of ringing on called lino by toll operator The toll operator can now at will start the automatic intermittent ringinglof the speciiic operating the ringing key 55 of her cord-pair,

or alternatively by momentarily depressing Y key 61 three times as will appear presently.

lli

Operating key applies alternating ringing current from source G over the traced talking path including conductors 231 and45, armature 362v and the bridged Winding of relay 363 in selector C. The relay 363 Which is vdesigned to be responsive to this type of current actuates and thus causes ground trom attracted armature 300 to be applied through armature 364 to the winding ot slow-releasing relay 365, the latter said relay operating to o'pen the ground from armature 339 Which is applied through the Wiper 314, and `iyhich said ground energizes relay 560 in the conncctor E.. The relay 340 is thus deenergized and deactuates in accordance with its releasing characteristic. This combined operation of relays 365 and 340 causes relay 560 in eon nector E to momentarily deactuate, the armature 369 on relay 340 in selector C retracting to close ground from armature 339 through y latter said armature to Wiper 314 to thereby limit the period of deaetuation of relay 560 in connector E tor an object which will appear presently, regardless of how long the operator may apply the ringing current by key 55 effective to maintaining relay 365 correspondingly actuated.

Having in mind that armature 548 is now attracted, when the armature 567 momentarily retracts fit unlocks the relay 546. Armature 540 being now attracted, ringing current from vsource G5 is 'applied through interrupter armature 582, armatures 540, 541, 542, Wiper 517, bank terminal 527, bell 581 of telephone T5, bank terminal 526, Wiper 516, armatures 544, 545, inside Winding of relay 546 to grounded battery, it'being noted that the `frequency of application of the source G5v throilgh theagency of interrupter il. 1s faster thanl when the source R5 was applied through the agency ot interrupter I. The source G5 has a dili'erent frequency ot alternation and other inherent characteristics, so that not only will the bell 531 of the called telephone T5 be rung faster or at different intervals than bell 543 but the bell 561 will be runt,r selectively so that only one or the other bell 581 tor calls from toll operator v and 543 for calls from a local subscriber) Will sound at any time to indicate the source dfthe call. That is. depending upon whetherlthe second antecedent selector is F or C will de'-l termine which bell 543 or 581 will be rung, respectively.

espuma on calle/Z Zine to toZZ operator call lock through armatures 547 and 567 to ground. This continues the talking path from armatures 545 and 541 through armatures 57 8 and 579 over the traced path to the upper and lower windings of relay 361 to grounded battery and ground, respectively. The relay 361 will actuate and the transmitter of telephone T5 will be energized through its windings.I The relativ'el low ohmic resistance involved in the Win ing of relay 301 in series with the impulse conductor 234 will be displaced by the relatively high ohinicresistance involved in the Winding of relay 302 without lapse of current over conductor 234, due to the attraction ot armatures 369 and 303, the armature 303 maintaining the relay 301 operatively energized. Duey t'o the 'substitution of the'windin of relay 302 for they Winding of relay 301', t e current traversing .the windingi'ot the relay 12 in the cord-pair is link circuit of the connection. The talking path from the jack J Will be overtlie heavy conductors of the cord-pair, conductors 231 and 45 leading-out from jack J through lselector B to the primary sections of the repeating coil in selector C, the armature 372 short-circuiting the condenser' between the c latter said windings. The talk-ing path from the secondary sections of the said repeatin coil to the called telephone has been trace The talking circuit through the cord-pair to the called telephone T5, other than the repeat-ing coil in selector C is thus clear of affecting attachments.

It will be noted, in this connection, that it the party -at telephone T5 replaces his receiver on the switch-hook the relay 361 in selector C will thereby deactuate and replace the Winding of relay 301 in the impulse circuit including condu'ctor 234, and under which condition the current traversing the winding ot'relay 12 will be augmented to its original operative value so that the lamp 16y will glow as a clearing signal. The tool operator may novv at Will re-ring on the called line as primarily, or she may alternatively restore the switches, as will appear presently.

Reatoratz'on of the switches by toll operator The restoration of the switch train i's made responsive to the toll operator withdrawing the plug P from the jack J. This opens the energizing circuit for relay 302, regardless of the condition of relay 361, and removes the recava? 9 ground from the release trunk at spring 17 and at other point-s consistent with the de actuation of relays 302 in selector C and 502 and 560 in connector E, so that relays338, 440 and'534 deactuate, together with obvious other relays. Selector C is restored responsive to ground being applied through armatures 307, 308 and 300, oil-normal springs to the release magnet designated (Rel. M.). Se-

1G, lectorD is restored responsive to ground being applied through armatures 450, 451, 452, oil'- normal springs to the release magnet (designated Rel. M.). Connector E is restored responsive to ground being applied through armatures 508, 509, ott-normal springs to the release magnet (designated Rel. M.). The

'foregoing releasing operations will take place whether the receiver is on' or'o the hook of telephone Tf".

Grilled line encountered busy in toll operato/r call Had the called line been busy when the wipers 515 to 517 were set upon the bank terminals 525 to 527, respectively, and therefore the lbanlr terminal 525 constituted ground potential, the busy relay 552 would actuate in the manner before described in a call from a subscriber, but due to the armature 568 being attracted (only under the condition of -a call by a toll operator) the latter said relay will be now locked through armature 551, spring 550, armature 535, spring 536, armature 568 and spring 569 to the release trunk. However, ground from armature 583 is applied through, spring 571, armature 572 to the upper winding terminal of relay 549 to cause the latter relay and relay 575 to actuate and lock and relay 549 to deactuate as and for the objects set forth when armature 570 caused such operation. Ground from armature 565 is `applied through armature 584 to the inside winding of relay 546, but to no operative object since relay 546 was locked responsive to th actuation of relay 528.

Armature 585 attracted subsequent to the actuation and locking of the relay 552, so that in place of the latter relay being locked to 4the release trunk as originally, itY is now locked by way of armatures 568, 585, 586, 532, spring 531, wiper 515' to the busy-ground ed private terminal 525. Under the condition the interrupted ground through the tone source transformer B5 will be applied through armatures 553, 554, and 587 to talka ing conductor 555 effective to periodically operate the relay 361 in selector C in correspondence with the speed of the interrupter l5. This will cause the cord-pair lamp 16 to correspondingly iash to indicate to the operator the continued busy condition of the called line. The'operator may also perceive the busy t'onefrom source B5 by operating the listening key L. The operator may withdraw the plug l, whereupon the switch train will be restored in the manner before described vwherrthe plug P was withdrawn.

From the foregoing, it is clear that when a toll operator directs the setting of the connector E upon the bank terminals of a called line the relay 534 will actuate to effect the seizure if it is idle, and the busy relay 552 will actuateto apply the busy signals if it is busy at the instant of selection. Moreover, only when a toll operator directs the selection of a called line will the relay 546 be caused to aotuate and lock before the called line is selected to disable the application of ringing current thereto until ringing current is applied from the cord-pair to initiate the ringing, as will appear presently. 'lhisl application of ringing current from the cord-pair may 'be at will manually directed, as will rst be described, or a. plied automatically-responsive to a manna presetting, as will be described thereafter. Still other methods for initiating the ringing will appear presently.

Further, it is clear that when the relay 534 actuates to effect the seizure or alternatively, when the relay 552 operates to apply the busy signals, the relay 575 in the connector will be locked and the relay 32 in the cordpair will be unlocked to exclude the calling device 40 and extinguish the lamp 42.

Buey called lane becomes z'clle If the toll operator elects to await the time when the called li'ne will become idle, she will be apprised of the idle condition by the steady glowing ot the lamp 16 respon sive to the busy ground on the private bank terminal changing to idle-battery potential, the relay 552 deactuating. However, there will now he no energized circuit to cause the operation of relay 534 because the upper terminal 'f'its outside winding extends through armatures 568 and 585, to retracted armature 586. That is, the connector E will not seize the now idle selected called line, so that the called line is unbarred to other connectors. This is so that if the toll operator is not ready to take 'the line upon it becoming idle it will not be needlessly held out of service.

Toll operator may] start ringing on selected alle called line at will The toll operator can at will cause the called line to be tested and rung upon if idle, or the busysignals applied perceptible to her if busy, responsive to momentarily ap# plying ringing current by the key This causes relay 560 to momentarily deactuate as before described. However it causes different operations in the connector than before due to the fact that the relay 534 is now deactuated, whereas it actuated in the assumed call wherein the called line was selected whemidle since armature 585, now attracted, was then retracted. .c

The retraction of armature 567 unlocks relay 546 asbefore described.' Firstassume the called line is now idle. The retraction of armature 568 causes release trunk ground to be applied through spring 536, armature 535, outside winding of relay 534, armature 532, spring 531, wiper 515-to idle battery on private terminal. 525, the-relay 534 actuating and locking. The attraction of armature 570 has no effective purpose at this time, since relay 57 5 is locked to the release trunk. The retraction of armature 567 lunlocks relay 546. Ringing current from source G will new be applied to the called line and the circuits are in the same condition as when the toll operator before caused 1t to be rung upon.

sezione @allee am; @geen any when an operator attempts to sia/rt ringing thereon New assume that the called line is again busy when the operator attempts to start ringing thereon. When the arma-ture 588 retracts, release trunk ground is applied through armatures 548, 588, spring 550, armature 551 to the winding of relay 552, the latter said relay actuating and locking through armature 535, spring 536t0 the release trunk. When armatures 588 and 568 attract the locking circuit is changed from the release trunk to a path including armature 568, make-spring 569, armatures 585, 586, spring 531, wiper 515 to the busy-ground on the private terminal 525.

The locking circuit for relay 552 under the kp last described condition included the armature 586 on relay 552, vand this armature retracts if the called line should again become idle, whereupon the cord-pair lamp 16 glows constantly. l The operator can then at will apply ringing current by the key. 55 to momentarily deactuate the relay 560 which will again cause the called line to be test-ed and seized by the actuation of relay 534 only if it is still idle, or alternatively cause relay 552 to again actuate if it has become busy.

Automatic seieurepf selected calleelline @wir vandaan @meg By closing the'switch-ariii 590 ground is applied to the resting contact of armature 586, and under this arrangement in case the busy condition of the selected called line terminates and the relay 552 deactuates resultant thereto a circuit is closed from ground, switch-arm 590, armature 586, spring 569, armature 568, spring 536, armature 535, out-. side winding Aol relay 534, armature 532, spring 531, wiper515 to idle battery on prip Relay 534 will actuate to effect seizure, relay 546 remaining locked. The'operator can 'now at will un- .tive feature is not desired.

Leonie? lock relay 546 to start ringing on the called line by operating key as if the called line had been first encountered idle, since the connector is in such condition. l

Object of limited retraction period of com certi/ng relay Due to the limited retraction period of relay 560 through the agency of relay 340 in selector'C the lamp 16 will be in condition to immediately flash if the selected line is not seized bythe connector underconditions as have been described, even though the toll operator may still have the ringing key 55 in operated position.' Uf course, the relay 340 may be dispensed with if the latter opera- In this connection, it will be clear that the armature 540and cooperating contacts may be transferred to the relay 560, or even to relay 549 if the resting contact of the spring 571 is madepermanently resting,'without alter ing the operative features of the system, though false operation of the bell 543 is possible while the relay 560 is deactuatedv if the armature 540 is placed on the latter said relay.

,The brief retraction period of relay 560 will make this objection almost non-existent, and in any event if the interrupters l and l are timed as shown in the drawings s0 that all rings from source R5 will be coincident with any ringing from source G5, the overlapping of the false ring while armature 540 may be retracted will not be noticed.

Ringing started automatically responsive to connector seizing on toll operator calls i Had the toll operatordesired to have the ringing automatically start responsive to the connector E seizing, key 65 would have been operated in place of key 19. That is, relay 66 would be operated in place of relay-22, way-down spring 67 causing relay 23 to actuate as when ke 19 was operated. Under the condition o relay 66 being. operated in place of -relay 22the relay 24 will not be operated. Then, when the connector is set upon the bank terminals of the called line,

y-vvhether it is idle 0r busy, and the relays 43 and 47 thereupon deactuate in sequence, as described before, ringing current from source G will lbe applied through armatures 69, 70,.

tip of plug tip of jack J Vand over the traced path including the bridged relay 363 in the `selector C and traced path to the ring l of jackvgl, ring bf plug l?, armature 44, winding of relay/'43 to grounded batter ,the relay 363 attracting its armature, but t e relay 43 remaining deactuated due to /its non-susceptibility to this ringing current. However, this circuit path will only endure until the rela 47 deactuates consistent with its releasing characteristic, to unlock the relay 32 in the manner as hereinbefore -described.

sufiicient to cause the required momentary deactuation of-relay 560 in the connector E to unlock relay 546 (which locked When relay 528 actuated) and thereby start the application of ringing current from surce G5 to the called line. y

Operation of 'pre-setting cord-pair ringing keys h In this connection it will be clear that when thekey 19 Was operated Way-down and released to its intermediate locked position and relay' 23-has had time. to deactuate consistent Witli -its`releasing characteristic, relays 43-and 47 are actuated, so that the trip- 'magnet will operate the shift-plate to restore thekey 19;'this operation `of the tripmagnet occurring within a fraction of a second after the toll operator releases the depressing pressure from the key button, but lon enoughto insure that the key 19 was hel csutciently to permit the relay 47 to actuate. That is, the shift-plate is used only to insure that the operator will not' be enabled to release the key too quickly. If the operator is instructed to hold the key depressed until lamp 53 glows, suilicien". time will have elapsed, and under this condition the shift-plate and trip-magnet will notv be required'. In the same manner, the operator would be instructed to hold key until the corresponding lamp 67 glows. The lamp 53 or 67 will glovv until the conneclor seizes to ing on the called ine she elected, since there are nooperated keys to indicate this, and she may desire to alter this predetermined method elected in the manneras will appear presently.

prompt the toll operator what kind of ring- Changing method of initiating' rz'ngz'ng after toll operator starts extension of caZl' If the toll operator when extending the call after setting the key 19 to employ di- 'rected at will ringing on the called line by i that current from source G will be applied effective to relay 363 in selector C responsive to relay 47 deactuating responsive to the connector being set upon the terminals of the called line. This will momentarily deactuate relay 560 in the connector to initiate the ringing on the called line if idle. However,`

if the called lineis bus the called line will not be seized because there will be 4no idle battery potential on the private terminal to energize the outside winding of relay 534 and the relay 552 (initially locked to the llt busy'ground) will be maintained locked to the release t-runk While armature 568 is retracted. The lamp 53 will extinguish and lamp 67 will glow responsive to the operation of the key 65.

Had the key 65 been operated initially, in place of key 19, and under Which condition the relay 24 Would not. be locked, the operator maychange the method of ringing on the called line by operating key 19 any time before the connector E is set upon the terminals of the called line. This Will cause relay 24 to actuate and lock, thus preventing the application ofthe source G for initiating the ringing on the called line. The key 35` may also be. employed to open the locking `circuit of relay 24 to thereby change from .Starting rin-ging by control over the imp/dse conductor The starting of ringing on the called line in the foregoing descriptions was through the agency of ringing current applied efective to relay 363 in selector C. 'When the call originates over a long toll line, particularly, the applying of ringing current effective to the relay 363 may have disadvantages, or at least introduce objectional expedients. The present invention contemplates an alternative method of initiating the ringing by momentarily interrupting the impulseV conductor three times. The latter said arrangement permits the number of said interruptions to be changed by altering the connection of a conductor of the auxiliary switch C.

At the time the connector is set upon the terminals of the called line and the relay 345 thereupon actuates, a circuit is prepared from the resting contact of `attracted armature 307 by the attraction of armature 375. Operating key 61 three times (having in mind the calling device 40 has already been excluded) will cause three ground impulses to be applied rom armature 307, armature 375, Winding of series slow-releasing relay 376 to the motor magnet (designated Mot. M.), causing it to correspondingly operate three times to s et the wipers 377 and '37 8 on bank terminals 379 and 380, respectively. Responsive to the first said impulse, the armature 381 will energize the slow-releasing relay 382, and the latter two relays will sustain until after the last of the three said impulses has been sent. Thus, the Wipers 377 and 378 are disconnected during their advancement. Wiper 378 becomes re-connected rst and ground is thereupon applied from armature 381, Wiper 378, bank terminal 380 to the Winding of relay 365, the latter relay actuating to momentarily open the energizing circuitffor relay 560 in the conclosed from grounded bank terminal 379,

armature 383 to the interrupter armature of the motor magnet, the motor magnet energizing in series with the winding of relay 37 6 and the wipers stepping forward to dead "bank terminals 384 and 385,'the energization of relay 365 beingbrief. The wipers will rest in this position until advanced by impulses applied fromarmature 307. That is, four bank terminal positions constitute a set and there may be a plurality of these sets in a row of p grh'aps 25 terminal positions,

the last'bank position terminals 386 and 387 being adjacent in wiper relation to the bank term1nals'388 and389.

The relay 376 energizes and vattract-s its armature when the motor magnet energizes (advancing its wipers upon deencrgization) so that a delay will occur after each step of the wipers when the motor magnet is operating under its own interrupter action until armature 383 retracts, since relay 382 will energize responsive to armature 381 attracting. This delay will not be objectionable since there normally would be but asingle step taken and, abnormally, as by a single opening of the key 61, but three steps would be required to bring thewipers to the first successive resting position as on dead bank terminals 384 and 385, for example.

The key 61 may be operated more than three times in succession without sulicient delay between operations to admit of relay 382 deactuating causing the wipers 377 and 378 to be stepped forward accordingly and then advanced to the first successiveresting position when the interruptions by the key 61 cease and armature 383 retracts.

If a single opening of the impulse conductor 234 by the operation of key 61 (or its equivalent) occurs as bythe operator withdrawing the plug l? to restore the switches, the retraction of armature 307 before the retraction of armature 375 would cause a single impulse to be applied through the co-operated with anantecedent toll selector' as A when the 'call is under control of a toll operator over a 'toll line, as will appear presently. This operation may occur` because the relay 301 will deactuate before the ground is removed from the release trunk vselector terminating the toll line, so

. line winding of repeating coil r2, winding o lay 239 in selector B is' energized. However,

if a selector like selector B is introduced intermediate between selector B and selector C this application of ground from spring 17 of jack will be required. Under the latter condition an extra digit in the called line number corresponding to said intermediate selector will be required.

on called line yby control over impulse conductor In view of the auxiliary switch C causing the operation of relay 560 in the connecter corresponding to that effected by the operallife-ringing tion of relay 363 in selector C, the re-ringing and re-testing operations described with reference to the application of ringing current by .ringing key 455 of the cord-pair will apply equally to any operation of the auxiliary switch C wherein wiper 378 is primarily set uppn a bank terminal connected as 380 and .38 n v Distant toll operator calling over toll line In the foregoing descriptions the toll Operator located contiguous to the local exchange containing the called line directed the extension of the call over a four-conductor trunk to the called line extending to telephone T5. The operation wherein the externsonv to said called line is directed from a toll operator located at a distance wherein a two-conductor toll line intervenes will be described.

The selector A is .a specific incomin toll nated. The remote toll operator' is provided with a plurality of connecting cordspairs, one of whlch having connecting plu s P2 and C2 is shown. These cord-pairs may ave any well known circuit arrangements in addition esigto the circuit arrangement associatedv with v the sleeve conductor which is specific to the present invention. 1

Initiation of call by distant toll operator The remote toll operator will initiate the line relay 254, armature 255 to battery having its positivepole grounded, the relay 251 moving its armature to cause lamp 257 to glow to indicate the impulse circuit is closed, relay 254 actuating. Slow-releasing releaserelay 258 will actuate from ground applied from armature 260 and armature 261 will apply ground to the release trunk 262. Armature' 263 prepares' a circuit for the marginal relay 265.

The remote toll operator will now operate the key K2 to substitute the impulse calling i device 267 for the relay 251, the lamp 257 extinguishing. The operator will now operate the sending device 267 to send one open .impulse corresponding to the first digit l of the telephone number of the called line.

Relay 254 will accordingly momentarily deactuate one time, its armature 260 sending a ground impulse through armature 270 and winding of slow-releasing series yrelay 271 to the vertical magnet (designated Vert. M.), causing the shaft 272 to step its wipers 273 to-27 6 into alignment with the first level of bank terminals. In view of the selective circuits of selector A being like-those in selector B, which-'has been fully described, it is not .thought necessary to recite the complete op-V eration of selector A in seizing the first set of idle bank terminals of the first level leading to selector C.

The switching relay 281 being now actuated, a circuit can be traced from ground,

winding of marginalfrelay 265, armatures 263 and 282, wiper 274, bank terminal278, im-l pulse conductor 234 to the winding of relay 301, relays 265 and 301 actuating. Armature 283 energizes slow-releasing relay 284. It will thus appear that when the operator sends the last four digits 1111 the relays 25,4, 265 and 301 will correspondingly vibrate, the Ielay 301 causing the selectors C and D and connector E to operate in the manner before described to select the called line leading to telephone T5. The relay 284 will sustain its armature during the retractions of armature 283. The attraction'of armature 300 will not affect the toll line beyond removing a slight unbalance due to the removal of ground from the lower talking conductor of selector A.

Oalled line emm'mtered busy in call extended by distant all operato/1*1 If the called line is encountered busy, the busy tone may be discerned by the operator listening in with her listenmg key (not shown), and due to the before described periodic operation of relay 361funder the busy condition, the relay 265 will correspondingly vibrate' its armatures due to its marginal characteristic. The Vperiedic opera tions of the relay 361 under the iniiuence of the interrupter Is at the connector are slow enough to permit the relay 284 to retract its armature responsive thereto, though it will when the called party hangs u not retract its armature responsive to the retractions of armature 283 when call directing impulses are sent from the device 267.

If the key spring 252 is restored the lamp 257 will again glow and it will appear that the lamps 286 and 257 will alternatively glow responsive to the armature 255 changing the polarity of current traversing the relay 251 to visually indicate the busy condition to the operator. This alternate fiashing of the lamps 286 and '257 will cease and lamp 257 will constantly glow when the busy condition terminates. The called line can now have ringing current applied to it at will under direction of the remote toll operator.

Ranging oa called lz'ne 'a1/nder direction of distant toll operator The remote toll operator may now operate her sending device 267 in accordance with the digit 3, thereby causing relay 301 in selector C to correspondingly vibrate. In view of relay 345 being actuated, this will cause the auxiliary switch C to energize relay 365 for momentarily deactuating relay 560 in the connector for the purposes before described, the. called line being thus rung upon if still idle, andthe busy signals re-applied if it has become busy again. The application of ringing current to the called line when idle will be the same whether it is first encountered busy or idle, since the momentary deactuation of relay 560 in the connector will not take place vuntil the remote toll operator directively operates the calling device 267. However, ringing current applied over the toll lineeft'ective to relay363 will have the',

same effect as the sending of digit 3 so far as momentarily deactuating relay 560.:

I.lespcmse on called Zine todz'stant toll operatar call f y When the called party. at telephone Ts responds the relay 361 will actuate and steadi- 'larity to relay-251 by the retraction of armature 255,*caus'evs' the lamp 257 to extinguish and lamp' 286 to glow. Of course, the lamp 286 may be dispensed with, and under that condition the prolonged extinguishment of lamp 257 will indicate the response on `the called line.A The reverse operation of relay 251 and glowing of lamp 257 will take place In this connection, it will when the relay 284 retracts or attracts its armature to change the polarity of current for energizing the relay 251 a lapse of current thrugh the windingof relay 254 will occur while`the armature 255 is passing from one cooperative contact to the other. However, thls lapse will not be of a duration that will cause operative upset, due to intermedihe noted that las ate relays introducing delays which will absorb the lapse before it becomes operatively effective to vitiate the call.

Restoration of the switches by the distant toll operator Tone to apprise toll operator 'when connector z's set upon terminals of called Zz'fne The tone source B3 is applied through armatures 391 and 392 to the lower talking conductor of selector C, audible to the toll op erator, responsive to the connector being set upon the called line terminals. rlhis tone will be disconnected at armature 392 responsive to the party on the called line removing his receivery and will again be applied responsive 'to his hanging it up, so that audible signal to the toll operator is given as to these conditions. The timing of the. tone sources is such that the tone from source B3 will not be applied coincident, or at least completely coincident, with the application of the busytone source B5 so as to avoid confusion in case the called "line is encountered ybusy' wherein both tones `will be applied. That is, tones-are non-coincidentallyl applied with respect to the periodic applications of each said tone, eii'ected through the interrupters I5 and I3.

The tone source M3, applied through the switch-arm 393 when the arm is set in its shown dotted position by the switch attendant, substitutes the low. resistance secondary winding of the said tone source transformer for the release trunk. This tone will be perceived by the toll operator as indicative that the selector C has been seized by the antecedent selector yin the concerned call extension. lt will be disconnected when the connector is set upon the terminals of the lcalled line at which time relay 345 actuates. The timing of this tone from source Ma will be consistent with the timing of tones from sources B9 and B5. That is, the interrupters I3, B3 and IM will be mounted on the same shaft and angularly displaced with respect to each other so that each corresponding tone will be solely operative during a certain portion of a revolution. The tones from the. said sources B, B8 and M3 will be distinctive in pitch or other quality.-

Preferred ,embodiment of selector D introdwing Fz'g. 6

By reference to Fig. 7 it will be noted that the group of selectors containing selector D show their first level divided into a group of seven first choice specilic local connectors of 4 any suitable well known type, and a second group of three second choice combination local and toll connectors containing connector E. The group containing specific lo-l cal selector F and the group containing specific toll selector C show their first level common to the groupcontaining selector D.'

by subscribers and toll operators and will therefore be 'fewer in number than if two groups were provided; one for each said class of calls. However, only aportion (3 to 7 of the connectors are combination local and toll connectors, since as will appear,'the combination local and toll connectors will be sole choice for calls directed by a tollroperator while these latter will be last choice for calls directed ,by a subscriber; all of the connectors of the two said groups being available for calls directed by a subscriber.

Combination local and toll connectors are inherently more expensiveand complicated than specific vlocal connectors, so it is advantageous to employ as small number of combination local and toll connectors as will safely carry the maximum toll traiiic. The number of specific local connectors may therefore be less than the number estimated to carry the maximum local or subscriber directed traiiic, relying on converting to local traffic uses such of the. combination local and toll connectors as may be required at such times of maximum local traflic and when there may not be a'maximum of toll traiiic.

Selector D dz'scrmz'nates on toll operator calls The-means for causing. the selectors a's D to discriminate'a'nd pass over idle bank terminals corresponding to speciiic local connectors and seize only an idle combination local and toll connector v-will be pointed out.

Having in mind that the selector D referred to in Fig. 7 has the circuit modifications shown in Fig. 6 introduced, it will be clear that only when a selector as D is seized be applied over. conductor 334 cam-spring 451 to wiper 4113 to place a false busy on the latter said wiper only while the wipers are passing-'over the first seven rotary bank positions indicated by the bracket 453, so that any idle specific local connector will be barred, and due to the cam-spring 451 being local and toll connector by aspeciic toll selector as C will ground 

